1. Field of the Invention
This invention relates to the formation of a glass run for slidably receiving the peripheral edge of a moving window glass so as to guide the movement of the window glass, for sealing between the window glass and a door sash, and for including an internal debris discharge system.
2. Description of Related Art
A conventional glass run 50 is shown in FIGS. 6 to 8. The glass run 50 is attached to a door sash 1 of an automobile (see FIG. 4) and seals between the outer peripheral edge of a raised (closed) door window glass 2 and the door sash 1. The glass run 50 comprises a plurality of straight extruded parts 51 and curved or bent molded parts 61, each of which connects together two of the straight extruded parts 51. The extruded part 51 is attached to a straight section of the door sash 1 while the molded part 61 is attached to a corner section of the door sash 1. The letter "S" designates aborderline, or the connected end surfaces, between the extruded part 51 and the molded part 61.
The extruded part 51 shown in FIG. 7 comprises a channel portion 54 which consists of a bottom portion 52, two side walls 53, and two seal lips 55 which project into the channel portion 54 from free ends of the both side walls 53. The molded part 61, shown in FIG. 8, comprises a channel portion 64 which consists of a bottom portion 62 having a solid flat interior surface, two side walls 63, and two seal lips 65 which project into the channel portion 64 from free ends of the both side walls 63. The end face of the outer peripheral edge of the door window glass 2 slides on the surfaces of the bottom portions 52,62. Therefore, there is a concern that the surfaces of the bottom portions 52, 62 may be easily abraded. Further, if debris such as sand or dust becomes inserted between the surfaces of the bottom portions 52, 62 and the end face of the window glass 2, abrasion of these surfaces will be accelerated in advance of normal conditions.
To solve the above-mentioned problem, gutters or ditches 57 are formed in the longitudinal direction along the interior of bottom portion 52 of the straight extruded part 51 with small cross sectional areas. Gutters 57 are formed simultaneously when the channel portion 54 and the seal lips 55 are formed by extrusion molding made of an ethylene-propylene-diene copolymer (EPDM) rubber to form the extruded part 51 as a single product, as shown in FIG. 7. With such a structure for the extruded part 51, debris moves and drops into the gutters 57 and is discharged when the window glass 2 slides on the surface of the bottom portion 52.
On the other hand, no gutter arrangement is formed on the interior surface of the bottom portion 62 of the molded part 61, as shown in FIG. 8. Therefore, as for the molded part 61, the above-described operation of discharging debris is not achieved. The reason why no gutter is formed for the molded part 61 is thought to be as follows. Namely, even if gutters having small cross sectional areas are to be formed, it is known that a bleeding mold release agent or process oil, or a generated vulcanization gas easily fills such gutters when the channel portion 64 and the seal lips 65 are molded from an EPDM rubber to form the molded part 61 as a single product. Therefore, no gutter has came to be actually formed.
Also, a molded rubber is inferior to an extruded rubber in durability, even though both are formed from the same type EPDM rubber.
Under those circumstances, there was a problem that the bottom portion 62 of the molded part 61 wore out easier and earlier than the bottom portion 52 of the extruded part 51.